Recently I was investigating alerts that were being generated for inbound interface discards on multiple interfaces and multiple Vyatta 5400 devices. There were not any noticeable performance issues on traffic passing through the devices. The discards would report in SNMP, show interface ethernet ethX, and ifconfig outputs. An example show interface ethernet ethX output I was reviewing is below. vyatta@FW01:~$ sh int ethernet eth0 eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000 link/ether 00:50:56:0x:0x:0x brd ff:ff:ff:ff:ff:ff inet 172.
I find the interface discard counter a deceptively complex counter. When you ask people what the counter means the usual answer is that you are over running the throughput capability of an interface. Which matched pretty closely to the definition in the IF-MIB SNMP MIB. The number of inbound packets which were chosen to be discarded even though no errors had been detected to prevent their being deliverable to a higher-layer protocol.